Derivative Instruments and Hedging Activities (Assets and Liabilities - Current vs. Noncurrent Derivative instruments) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Derivatives, Fair Value [Line Items]
Total asset derivatives	$ 240	$ 100
Total liability derivatives	371	602
No Longer Carried At Fair Value
Derivatives, Fair Value [Line Items]
Total asset derivatives	169	186
Total liability derivatives	190	191
Contracts Subject To Netting Arrangements
Derivatives, Fair Value [Line Items]
Total asset derivatives	91	25
Total liability derivatives	314	522
Derivative Assets Not Offset Under Netting Arrangements	(9)	(9)
Derivative Liabilities Not Offset Under Netting Arrangements	(9)	(9)
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	(3)	0
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(6)	(5)
Derivative Asset	79	16
Derivative Liability	299	508
Current
Derivatives, Fair Value [Line Items]
Total asset derivatives	32	14
Total liability derivatives	157	178
Noncurrent
Derivatives, Fair Value [Line Items]
Total asset derivatives	208	86
Total liability derivatives	$ 214	$ 424